mouseDragged(MouseEvent e)
Set the models value to the position of the thumb's top of Vertical
scrollbar, or the left/right of Horizontal scrollbar in
left-to-right/right-to-left scrollbar relative to the origin of the
track.

mousePressed

If the mouse is pressed above the "thumb" component
then reduce the scrollbars value by one page ("page up"),
otherwise increase it by one page. If there is no
thumb then page up if the mouse is in the upper half
of the track.